Hide subsurf modifier curve in edit mode
To disable the modifier only in edit mode press the cube icon:

You can also:

Enable the Deformed display which deforms the edit mode mesh to the subserfed object, making it easier to see geometry. Note that this can make tools like loopcut and knife hard to use, you may have to disable it to use those accurately.


Disable the modifier in the viewport by clicking the eye icon (affects object mode too). This will not affect the render. To disable the modifier in the render, click the camera icon.